Mars
* Heroes with high magical or pure damage will bypass Bulwark: 
Timbersaw, 
Dark Willow, 
Enigma, 
Invoker, 
Pugna, 
Skywrath Mage, 
Tinker, 
Zeus, 
Oracle.
Primal Beast
* Oracle can negate and shut down Primal Beast simply with Fate's Edict, especially in the early game, as a majority of his damage-dealing spells are magic.
* Oracle can interrupt Primal Beast's 
Onslaught charge with a well-timed Fortune's End.
* Primal Beast's lethal burst damage combos can be further stalled with False Promise; combined with Fate's Edict and regen from Purifying Flames, Oracle can even completely negate Primal Beast's offense.
Additional:
* 
Fate's Edict completely negates all of Primal Beast's major damage-dealing spells in the early game and can render Primal Beast useless when cast on a target he is focusing, or in Oracle's defense against Primal Beast himself.
* 
Fortune's End keeps Primal Beast in place, especially while trampling or in the middle of an Onslaught charge.
* 
False Promise can interrupt Primal Beast's abilities, as well as further delay Primal Beast from dealing lethal burst damage. In combination with Fortune's End, Oracle can potentially save an ally from Primal Beast's spell combos.
Mars
* 
Arcane Orb's pure damage ignores Mars' Bulwark.
* 
Astral Imprisonment can be used to stop Mars from being disruptive or save allies from his abilities.
* 
Sanity's Eclipse deals high damage to Mars, due to his low intelligence pool.
Primal Beast
* Primal Beast is mostly played in the offlane role, so picking a carry who can escape from him is essential. Heroes such as 
Troll Warlord, 
Lone Druid and 
Outworld Destroyer, or generally any carry with a stun, slow or ability to fight back will stop him from having the good start he needs.
Mars
* Heroes with high magical or pure damage will bypass Bulwark: Timbersaw, Dark Willow, Enigma, Invoker, Pugna, Skywrath Mage, Tinker, Zeus, Oracle.
Primal Beast
* 
Malefice will prevent Primal Beast from doing anything for a long duration even in the early game when at his strongest.
* 
Midnight Pulse will scale with his max health so will do a ton of damage combined with any generic stun or Enigma's own abilities.
* Primal Beast relies completely on mobility to do damage, 
Black Hole makes sure he cannot use any abilities or threaten heroes he is typically good against.
Mars
* It is difficult for Mars to trade blows with Ogre Magi in the early game thanks to his high base health, resistance and 
Ignite.
* 
Bloodlust can assist Ogre Magi or an ally in repositioning against Mars for its move speed bonus.
* 
Fireblast can interrupt and mitigate Mars from performing his skill combos, especially in combination with 
Multicast.
Primal Beast
* Supports who can slow him to the point Trample does very little damage in the lane are also not fun: 
Lich, 
Ogre Magi, 
Winter Wyvern.
Mars
* Heroes with high health especially Strength heroes will take more damage on Sun Ray: 
Axe, 
Pudge, 
Bristleback, 
Mars.
Primal Beast
* Primal Beast is disarmed during Trample so will be unable to destroy a 
Supernova no matter how close it is to him.
* The same ability can also be used to save allies with the help of an 
Aghanim's Scepter.
* 
Sun Ray will do thousands of damage to Primal Beast if surviving a full channel time due to his high health scaling for the ability.
* 
Icarus Dive is a fantastic way to escape Primal Beast after he has used Onslaught.
* Phoenix has a naturally very high health pool making it hard for Primal Beast to deal with him with his magical damage.
Mars
* Heroes with high magical or pure damage will bypass Bulwark: Timbersaw, Dark Willow, Enigma, Invoker, Pugna, Skywrath Mage, Tinker, Zeus, Oracle.
Primal Beast
* Invoker's numerous area-of-effect abilities can interrupt Primal Beast, especially while he is in the middle of a team fight, where Primal Beast thrives. (
Tornado, 
Cold Snap, and 
Ice Wall all help to disable Primal Beast and control him from a distance.
* 
E.M.P. disintegrates Primal Beast's low mana pool.
* However, Invoker is quite a slow-paced hero and not particularly known for being survivable against a rampaging Primal Beast with 
Black King Bar.
Mars
* 
Firestorm and 
Pit of Malice are very disruptive in team fights, completely matching Mars especially since it can all be cast inside Arena Of Blood and also does percentage-based magical damage, negating Bulwark.
* 
Dark Rift can save any allies of Underlord trapped in Arena Of Blood.
* 
Atrophy Aura allows Underlord to lane against Mars quite well since he does not have the best base damage during the early game.
* Underlord is a common carrier of both 
Pipe of Insight and 
Mekansm/
Guardian Greaves, allowing his team to combat Mars in the mid to late game.
Primal Beast
* Pit of Malice is very good at preventing Primal Beast from entering the fight and stopping Trample damage at all stages of the game.
Mars
* Heroes with strong area-of-effect damaging and/or disabling abilities will be able to intercept Underlord and his team when they exit from Fiend's Gate: 
Luna's Aghanim's Scepter upgraded 
Eclipse, 
Dawnbreaker's 
Solar Guardian, Axe's 
Berserker's Call, Mars's 
Arena of Blood, 
Jakiro's 
Macropyre, 
Dual Breath and 
Ice Path, 
Naga Siren's 
Song of the Siren, 
Razor's 
Eye of the Storm and 
Plasma Field, 
Lina's 
Light Strike Array, 
Broodmother's 
Spinner's Snare from Aghanim's Scepter, 
Elder Titan's 
Earth Splitter and 
Echo Stomp, 
Alchemist's 
Unstable Concoction and 
Acid Spray, 
Queen of Pain's 
Sonic Wave, 
Dark Seer's 
Wall of Replica and 
Vacuum, 
Venomancer's 
Noxious Plague and 
Poison Nova from Aghanim's Scepter, Oracle's Fortune's End and 
Rain of Destiny from 
Aghanim's Shard, 
Bloodseeker's 
Blood Rite, Enigma's Black Hole and Midnight Pulse, 
Shadow Fiend's 
Requiem of Souls, 
Batrider's Aghanim's Scepter upgraded 
Flaming Lasso, 
Firefly, 
Flamebreak and 
Sticky Napalm, 
Ancient Apparition's 
Ice Blast, 
Sand King's 
Epicenter, 
Sand Storm and 
Burrowstrike, 
Gyrocopter's 
Call Down, 
Ember Spirit's 
Sleight of Fist, 
Death Prophet's 
Exorcism and 
Silence, 
Monkey King's 
Wukong's Command, 
Crystal Maiden's 
Freezing Field, 
Muerta's 
The Calling, 
Medusa's 
Stone Gaze, Zeus's 
Nimbus from Aghanim's Scepter. Dark Willow's 
Bramble Maze, 
Pangolier's 
Swashbuckle, 
Grimstroke's 
Soulbind, 
Ink Swell and 
Stroke of Fate, 
Earthshaker's 
Echo Slam and 
Fissure, 
Puck's 
Dream Coil and 
Waning Rift, Winter Wyvern's 
Winter's Curse, 
Magnus's 
Reverse Polarity.
Mars
* Nukers who have set amounts of damage will really struggle against Lone Druid especially in True Form: Puck, 
Void Spirit, Mars.
Primal Beast
* Primal Beast is mostly played in the offlane role, so picking a carry who can escape from him is essential. Heroes such as Troll Warlord, Lone Druid and Outworld Destroyer, or generally any carry with a stun, slow or ability to fight back will stop him from having the good start he needs.
Mars
* Heroes with break abilities: 
Shadow Demon (with Aghanim's Scepter), 
Viper.
Primal Beast
* Primal Beast really suffers against supports he cannot bully in the lane: this includes 
Dazzle, Shadow Demon and Dark Willow since they can use their respective abilities to stop Primal Beast from dealing burst damage, or make it hard for him to stay in range.
Mars
* Heroes with high magical or pure damage will bypass Bulwark: Timbersaw, Dark Willow, Enigma, Invoker, Pugna, Skywrath Mage, Tinker, Zeus, Oracle.
Primal Beast
* Primal Beast really suffers against supports he cannot bully in the lane: this includes Dazzle, Shadow Demon and Dark Willow since they can use their respective abilities to stop Primal Beast from dealing burst damage, or make it hard for him to stay in range.
Mars
* Heroes that can save their allies can be a big problem for Mars: Dazzle, 
Omniknight.
Primal Beast
* Primal Beast really suffers against supports he cannot bully in the lane: this includes Dazzle, Shadow Demon and Dark Willow since they can use their respective abilities to stop Primal Beast from dealing burst damage, or make it hard for him to stay in range.
Mars
* 
Decay, 
Soul Rip and 
Flesh Golem all deal magical damage which ignores Bulwark.
* Decay reduces Mars' natural strength and therefore his health pool, which is what he relies on to trade effectively in lane.
Primal Beast
* 
Power Cogs keeps Primal Beast pinned down, preventing him from doing damage with Trample. Primal Beast's slow attack speed makes it hard for him to break the cogs and get away. In addition, Power Cogs' knockback is forced movement and thus will intercept Primal Beast's Onslaught if placed well.
* 
Battery Assault on a lone Primal Beast in the early game effectively keeps him from winding up Onslaught or basic attacking.
* 
Rocket Flare and 
Jetpack (from purchasing Aghanim's Shard) give Clockwerk many options to scout for Primal Beast, whose kit benefits greatly from ambushing.
Mars
* 
Dragon Slave deals reliable magic damage during the laning phase against Mars.
* Lina's 
Eul's Scepter of Divinity and Light Strike Array combo can interrupt Mars from being disruptive for a decent amount of time and leave him vulnerable for follow up stuns.
* 
Laguna Blade deals massive magical damage, and pure damage with Aghanim's Scepter.
Mars
* Rebound allows her to jump in or out of the Arena Of Blood. She can save her allies from the Arena with Dispose as well.
Mars
* 
Nethertoxin breaks the damage block from Bulwark.
* 
Poison Attack and 
Viper Strike's slows make it difficult for Mars to contribute to fights due to his low mobility.
Additional:
* Viper Strike can disable 
Bulwark entirely, making Mars far less tanky. Using Nethertoxin inside Arena of Blood may discourage enemies from following up with Mars's initiation.
* 
Rod of Atos is currently common on Viper and keeps Mars in position long enough to be killed.
* However, Viper is not very tanky earlier in the game, so positioning against Mars is important for Viper since a well-timed 
Spear of Mars can be the end of Viper.
Primal Beast
* 
Glimpse can prevent Primal Beast from initiating for most of the game with Onslaught.
* While 
Static Storm is not much of a threat in terms of damage, it does prevent Primal Beast from casting any spells for a long period of time if also trapped in 
Kinetic Field.
* Overall, Disruptor forces Primal Beast to buy a Black King Bar much earlier than he might like but becomes a major threat to Disruptor once he does.
Mars
* Solar Guardian can save allies caught inside Arena of Blood.
Mars
* 
Shadowraze deals magic damage and ignores Bulwark.
* Requiem of Souls deals magic damage and can fear Mars away, forcing him to turn around and therefore become vulnerable.
Mars
* Necrophos' largely magical damage completely ignores Bulwark.
* 
Ghost Shroud protects Necrophos from God's Rebuke but more importantly stops Mars from being a threat in lane.
Mars
* 
Ball Lightning makes it almost impossible to catch Storm Spirit without someone else initiating for you.
* 
Overload is not reduced by Bulwark and the magical damage spam can wear down Mars quickly.
Additional:
* Storm Spirit's abilities all do magical damage, which can bypass Bulwark.
* Ball Lightning can escape through Arena of Blood and it is easy to dodge Spear of Mars.
Mars
* 
Burning Spear's magical damage is very troublesome for Mars in the laning stage.
* 
Life Break's percentage-based magical damage bypasses Bulwark, and can also be used to jump in or out of Arena Of Blood.
Mars
* Mars' own father is a formidable foe because Zeus deals massive amounts of magical damage. The high damage, low cooldown nukes of 
Arc Lightning and 
Lightning Bolt combined with the percent health magic damage of 
Static Field will shred Mars' health because it bypasses Bulwark completely.
Primal Beast
* Soulbind prevents Primal Beast from being able to use Onslaught or his abilities to great effect for a lengthy amount of time.
* 
Phantom's Embrace is very difficult for Primal Beast to remove due to his slow attack speed and Trample preventing him from attacking.
Mars
* 
Snowball can protect Tusk and his teammates from a Spear of Mars' stun after an Arena of Blood, and with proper targeting, even bring them out of the Arena. This is especially noticeable in the earlier stages of the game before allies buy Black King Bar and rely on this less. Even during the late-game, Tusk can purchase a 
Blink Dagger to save allies that are caught before Black King Bars can be used by Blinking in and Snowballing out.
* 
Tag Team is a constant threat to Mars in-lane, as it deals significant damage and slow, making Bulwark slightly ineffective.
* It is worth noting that 
Ice Shards can be detrimental to Tusk's own team by creating terrain that Spear of Mars can latch on, though using it conservatively is a good enough solution in most cases.
Mars
* Swashbuckle is an auto attack and therefore ignores Mars' Bulwark.
* 
Shield Crash upgraded with Aghanim is an auto attack and therefore ignores Mars' Bulwark.
* 
Rolling Thunder makes him immune to magic, making Pangolier able to roll in and out of Mars' Arena Of Blood.
Mars
* Venomancer's spells all deal magical damage, ignoring Bulwark.
* Venomancer's multiple slows are especially effective at kiting Mars.
* 
Plague Ward can attack through Arena Of Blood.
Additional:
* Venomancer's poison attacks are all magical damage, ignoring Bulwark.
* Venomancer's multiple slows are especially effective against Mars' low mobility.
* Plague Wards can attack through Arena of Blood.
Mars
* Sticky Napalm slows turn rate, making it difficult for Mars to face frontwards, where Spear of Mars and Bulwark are effective. In combination with Firefly, which deals magic damage, Batrider can make quick work of Mars.
* Flaming Lasso disables Mars while enemies re-position themselves behind Mars to avoid Bulwark.
Mars
* Heroes with high magical or pure damage will bypass Bulwark: Timbersaw, Dark Willow, Enigma, Invoker, Pugna, Skywrath Mage, Tinker, Zeus, Oracle.
Primal Beast
* Heroes who can do scaling health damage to Primal Beast are very threatening for the hero. Such as: 
Phoenix, Tinker etc.
Primal Beast
* Heroes with unorthodox escapes will struggle against Primal Beast, such as 
Nature's Prophet, Tinker, and 
Templar Assassin.
Mars
* 
Ursa is a special mention because despite Bulwark diminishing most of the damage Ursa does, he is quite durable, especially with 
Enrage, discouraging the aggressive all-in playstyle of Mars; Ursa can simply not target Mars.
Primal Beast
* Supports who can slow him to the point Trample does very little damage in the lane are also not fun: Lich, Ogre Magi, Winter Wyvern.
Primal Beast
* Like above, supports with reliable stuns can be a massive problem and force Black King Bar in fights unideally, such as 
Shadow Shaman, 
Lion, 
Nyx Assassin.
Mars
* Heroes that depend on disrupting fights with ability combos or big ultimate abilities are vulnerable to the long stun of Fiend's Grip: 
Disruptor, Death Prophet, Enigma, 
Faceless Void, Invoker, Lich, Magnus, Mars, Medusa, Outworld Destroyer, Phoenix, Puck, Queen of Pain, Shadow Fiend, 
Treant Protector, 
Underlord, Winter Wyvern, 
Witch Doctor, Zeus.
Mars
* 
Kunkka's 
Ghostship and 
Torrent disrupt fights in Arena Of Blood.
Primal Beast
* Any ganking heavy support can be a big problem for Primal Beast, such as: 
Earth Spirit, Grimstroke before he has a Black King Bar.
Mars
* Heroes with high magical or pure damage will bypass Bulwark: Timbersaw, Dark Willow, Enigma, Invoker, Pugna, Skywrath Mage, Tinker, Zeus, Oracle.
Primal Beast
* Like above, supports with reliable stuns can be a massive problem and force Black King Bar in fights unideally, such as Shadow Shaman, Lion, Nyx Assassin.
Mars
* Heroes with high magical or pure damage will bypass Bulwark: Timbersaw, Dark Willow, Enigma, Invoker, Pugna, Skywrath Mage, Tinker, Zeus, Oracle.
Primal Beast
* Like above, supports with reliable stuns can be a massive problem and force Black King Bar in fights unideally, such as Shadow Shaman, Lion, Nyx Assassin.
Primal Beast
* 
Borrowed Time allows him to both exit his stuns prematurely and turn Trample into healing for himself. His Aghanim Scepter only prevents the automation of the spell, Abaddon himself can still manually activate it.
* 
Aphotic Shield will immediately debuff any stuns Primal Beast has put on allies but won't stop him from being stunned if casted on Abaddon.
Mars
* Heroes who cannot fight back during Arena of Blood in the early and mid game: 
Abaddon, 
Anti-Mage, Broodmother, Luna, 
Sniper, Troll Warlord, 
Weaver, 
Clinkz.
Mars
* Berserker's Call forces Mars to face in the direction choosen.
* 
Counter Helix deals pure damage and can go through Bulwark.
Primal Beast
* Long lockdown is a great way to deal with Axe to prevent Berserker's Call from being used, heroes such as 
Legion Commander, 
Beastmaster and 
Primal Beast are good examples of this.
Additional:
* Berserker's Call will be a stun for Primal Beast and not much else due to Trample making him unable to attack.
* 
Battle Hunger is neglitable because Primal Beast has a much bigger health than Axe, so he does not need to fear being slowed, or his other abilities including Counter Helix or even a 
Blade Mail.
* Getting Primal Beast low enough to use a successful 
Culling Blade can be very difficult due to his massive health advantage over most heroes.
* Not ability related but Primal Beast does not need to fear Axe in lane, as Trample, combined with Uproar and Onslaught will do a ton of damage even if Axe has a 
Vanguard.
Mars
* 
Rage, acting as a pseudo-Black King Bar, completely negates Mars' initiation if used in time.
* 
Feast does damage and heals based on max health, perfect against high-health strength heroes like Mars.
* 
Infest allows Lifestealer to potentially save allies from Mars' initiation with a quick burst of extra health.
Primal Beast
* Special mention to 
Lifestealer who can use Rage to prevent Trample damage, but Primal Beast's ultimate can still be casted during the spell.
Primal Beast
* The ensnare from melee 
Berserker's Rage can prevent Primal Beast from dealing further Trample damage and can allow Troll Warlord to relentlessly build 
Fervor on him.
* 
Whirling Axes (Ranged) can slow down Primal Beast while trampling and allow Troll Warlord to better control him from range.
* 
Whirling Axes (Melee) can blind Primal Beast if he attempts to auto-attack Troll Warlord after a fully charged Uproar.
* 
Battle Trance will make Primal Beast a sitting duck should he be rooted and attacked to death.
Mars
* Heroes who cannot fight back during Arena of Blood in the early and mid game: Abaddon, Anti-Mage, Broodmother, Luna, Sniper, Troll Warlord, Weaver, Clinkz.
Mars
* 
Blink Strike gives bonus backstab damage and can bypass Bulwark. Defensively, it could be used to teleport away from Mars, especially while inside Arena of Blood.
* 
Smoke Screen can interrupt Mars' skill combos, especially when cast inside Arena of Blood.
* 
Tricks of the Trade can be used to evade Mars' skills, which have a slight delay to them. It could also be used to buy himself time while trapped inside of Arena of Blood.
Additional:
* Bulwark is generally irrelevant against Riki as he primarily deals bonus damage from behind.
Mars
* Heroes who rely on their target to run away: 
Riki, 
Bounty Hunter.
Mars
* Bulwark negates most of the physical damage from Terrorblade and his illusions.
* God's Rebuke and Spear of Mars can decimate Terrorblade's illusions quickly.
Primal Beast
* Terrorblade has no stun and is vulnerable to Primal Beast's spell comboes due to his low health points in the laning stage and mid game.
* 
Reflection can be dispelled using Primal Beast's level 15 left talent.
* 
Sunder is the only real threat Terrorblade has against Primal Beast but he may die before he can even use it.
Mars
* Even if he can slow Mars down with 
Shrapnel and 
Headshot, Mars can tank Sniper's physical damage simply by facing him with Bulwark, allowing him to endure his auto-attacks into the late-game. Should Sniper choose to attack someone else, Mars can redirect his projectiles with Bulwark's active ability.
* Sniper's poor mobility makes him very vulnerable to Arena of Blood, especially in the early game. Mars can also take advantage of this by pushing him closer to the front line with Spear of Mars.
Primal Beast
* Primal Beast is one of Sniper's greatest counters, as he has no real means of escape and is very squishy, especially in the early game. Sniper's potshots and Shrapnel can contribute to Primal Beast's Uproar and further make him tankier than he already is. Onslaught allows him to close the gap on Sniper at his own volition, and Trample can deal serious damage to his meager health pool.
Mars
* Spectre cannot have a good game if she is pressured heavily in lane, which is something Mars can do. He may even force her to cast 
Haunt as an escape, putting it on a long cooldown.
* Should Spectre get to the late game, Mars can block a large amount of her damage with Bulwark and can mitigate some of the chaos caused by her Haunt illusions with God's Rebuke.
Primal Beast
* 
Dispersion reduces damage based on a percentage, which is very minimal against large amounts of small instances of damage such as Trample. It reduces each tick by about 14 at the maximum level, which is very small.
* 
Desolate is never a threat to Primal Beast due to his large health pool and Uproar is still out-damaging the ability.
* Onslaught can allow Primal Beast to chase Spectre fleeing with 
Spectral Dagger, as both skills phase through trees and terrain.
* Primal Beast can also dispel Spectral Dagger's slow with his left level 15 talent, making it completely useless against him.
* Primal Beast excels at early aggression, pushing weak carries out of lane and farming areas he wants to control. Overall just not a pleasant matchup for Spectre.
* Should Primal Beast buy an Aghanim's Scepter he can also break both passive abilities.
Mars
* Bulwark blocks much of Slark's basic attack damage, even during 
Shadow Dance.
* Slark finds it very difficult to have a good early/mid game when pressured in the early game by Spear of Mars and God's Rebuke.
* Spear of Mars and God's Rebuke can hit Slark through Shadow Dance and 
Depth Shroud.
* Should 
Pounce be on cooldown, Slark is very vulnerable inside Arena of Blood.
Primal Beast
* 
Dark Pact, Shadow Dance and Depth Shroud will do nothing against Onslaught and Trample, as they are both ground area-of-effect spells.
* Primal Beast has a gigantic hitbox, which could be difficult for Slark to escape with Pounce should Primal Beast choose to block him. Pounce also does not completely prevent Primal Beast from trampling offensively, as he still has some room to move.
* Primal Beast has a huge health pool making it difficult to shed it with 
Essence Shift and may allow Primal Beast to build Uproar stacks against him very rapidly.
* If Primal Beast buys an Aghanim's Scepter he can also break Essence Shift from working on attacks which is a big part of Slark's damage output.
Mars
* Bulwark mitigates 
Omnislash which deals physical damage, severely reducing its damage.
* Omnislash switch to opposite direction with each slash, so Mars can easily reduce most of its damage.
* However because {Ability ID:Blade Fury|Juggernaut} gives spell immunity Juggernaut can easily escape from {Ability ID:Arena Of Blood|Mars}.
Additional:
* Juggernaut deals mostly physical damage, which is easily mitigated with Bulwark.
* Juggernaut's Omnislash switches to opposite directions which each slash, so Mars can mitigate most of its damage since he only takes full damage from one direction: his back.
Primal Beast
* Primal Beast can use Uproar to tank a portion of Omnislash, making him much more likely to survive it. Primal Beast can also charge away from Omnislash using Onslaught as the spell ends.
* 
Blade Fury will never do more damage than Uproar once the stacks are activated.
* Primal Beast is very commonly buying items that are good against Juggernaut, such as 
Ethereal Blade and 
Heart of Tarrasque.
* Primal Beast has one of the few ultimates that can prevent Juggernaut from spinning away with a teleport.
Mars
* Phantom Assassin's high physical damage is greatly reduced by Bulwark.
* God's Rebuke has true strike, ignoring the evasion from 
Blur.
Primal Beast
* Phantom Assassin is known to be weak against bursts of magical damage, something Primal Beast excels at from the beginning of the game. He can use this to his advantage by constantly hunting Phantom Assassin down, especially if she is left alone to farm.
* Primal Beast is a good carrier of Ethereal Blade, Vanguard and 
Shiva's Guard all of which are very good against 
Coup de Grace and 
Phantom Strike.
* Even though Primal Beast does a lot of physical damage early on, later once Blur becomes more potent, she may find herself being overwhelmed by Trample and Onslaught instead.
* Primal Beast's ultimate goes through spell immunity and his level 25 talent makes it even more devistating against Phantom Assassin.
* Primal Beast can dispel 
Stifling Dagger and any attack modifers it applies with his left level 15 talent.
Mars
* Any hero who can counter-initiate in anticipation without getting caught in Reverse Polarity: 
Sven, Omniknight, Enigma, Luna, Naga Siren, Mars, Jakiro, Venomancer, Elder Titan, Faceless Void, 
Rubick, 
Keeper of the Light, Pugna, Invoker, 
Spectre, Alchemist, Treant Protector, Lina, Oracle, Zeus, Shadow Shaman, Phoenix, Razor, 
Huskar, Batrider, Kunkka, 
Tidehunter, 
Wraith King, Sand King, Medusa, Dawnbreaker.
Primal Beast
* Magnus is not tanky and struggles against burst damage, something Primal Beast excels at in the early-to-mid game. Primal Beast is also able to out-damage Magnus's 
Empower and can even contribute to his Uproar stacks.
* Using 
Skewer to drag Primal Beast while he is trampling will count as movement and will trigger a rapid number of slams, which could prove lethal to Magnus.
Mars
* Heroes who lack burst damage will have a hard time against Mars: 
Phantom Lancer, Nature's Prophet, Lich.
Primal Beast
* 
Sprout gets destroyed by Trample and Onslaught.
Mars
* Heroes who cannot fight back during Arena of Blood in the early and mid game: Abaddon, Anti-Mage, Broodmother, Luna, Sniper, Troll Warlord, Weaver, Clinkz.
Primal Beast
* Primal Beast has a massive healthpool making it very difficult to get through it with a nuke such as Eclipse or 
Lucent Beam.
* Primal Beast is faster than Luna, as one of her main ways to escape danger, is very problematic for her in the laning stage especially.
* His ultimate goes through debuff immunity, making Luna's Black King Bar less effective.
* Primal Beast commonly buys Blade Mail which is a big problem for a single target bursting hero like Luna.
Mars
* As long as Mars is facing her with Bulwark, even if pushed away with 
Gust, Drow Ranger will do no effectual damage against him. Mars' ability to endure her onslaught usually gives him enough time to cast Arena of Blood, of which she has a very slim chance surviving without Gust.
* With Bulwark's active ability, Mars can protect allies pursued by Drow Ranger by redirecting her projectiles to his shield instead.
Primal Beast
* Heroes who have low or high armor but very high health will be difficult for drow to burst down quickly: Primal Beast, Axe, 
Centaur Warrunner.
Mars
* Heroes who cannot fight back during Arena of Blood in the early and mid game: Abaddon, Anti-Mage, Broodmother, Luna, Sniper, Troll Warlord, Weaver, Clinkz.
Primal Beast
* While Broodmother can hide in the trees with 
Spin Web, Primal Beast's ability to trample trees down can give him an edge in catching her.
* 
Insatiable Hunger will not do much vs Primal Beast's onslaught of disables.
* While 
Silken Bola can slow Primal Beast down, it's not enough to stop Trample from doing more damage than Broodmother can do back.
* 
Spawn Spiderlings will be destroyed by Onslaught and Trample very easily.
Mars
* Durable heroes: Axe, Dawnbreaker, Bristleback, Mars, Omniknight, Tidehunter, Wraith King, Primal Beast, Underlord.
Primal Beast
* Heroes who rely on burst damage with magical damage will struggle to kill Primal Beast: 
Spirit Breaker, Gyrocopter, 
Leshrac
Primal Beast
* 
Pierce the Veil does not prevent Primal Beast from using any of his spells to their fullest and is one of the few heroes that can disable her during her ultimate and a common Black King Bar purchase. She will also likely be fatal to herself if Primal Beast has a Blade Mail active.
* 
Gunslinger will be disabled if Primal Beast buys an Aghanim's Scepter.
Mars
* If visible, Mars can knock Monkey King off his 
Tree Dance with God's Rebuke, as well as Spear of Mars. Arena of Blood also destroys a large swath of trees, which can disrupt Monkey King's positioning and turn him vulnerable should he choose to hide in trees.
* Mars can endure 
Jingu Mastery attacks simply by facing him with Bulwark.
* Mars can end Wukong's Command early by displacing Monkey King with a well-thrown Spear of Mars. Mars can also endure most of his clones with Bulwark.
Additional:
* Monkey King's natural reliance on trees makes him an exceptionally prime target for Spear of Mars. Should Monkey King use Mischief to disguise himself, it will still hit him, stunning him in the process.
* 
God's Rebuke easily pushes Monkey King out of Wukong's Command.
Primal Beast
* Onslaught prevents all of Razor's abilities from being effective against him, especially in the laning stage.
Primal Beast
* Since Primal Beast is highly mobile with Onslaught alone, he will be difficult to catch with both 
Cold Feet and Ice Blast.
* Ice Blast is less effective due to Primal Beast's massive health pool and resistance to taking damage.
* While 
Chilling Touch can be used to slow Primal Beast briefly, it is not enough to beat him back, and can also contribute to his Uproar stacks.
* Primal Beast has a dispel talent at level 15 that will remove Cold Feet immediately when Uproar is used.
Mars
* Bulwark blocks the attack from Meepo and his clones.
* Spear of Mars & God's Rebuke prevents Meepo and his clones from initiation or escaping.
Mars
* Medusa's Stone Gaze forces Mars to choose between getting petrified, or turning his vulnerable back on Medusa.
Mars
* Bulwark can make each of Medusa's attacks target him instead, reducing Medusa's contribution on team fights.
* Spear of Mars stuns Medusa and also pushes her away from teamfights, taking advantage of Medusa's low mobility.
* Arena Of Blood blocks Medusa's attacks from outside the arena.
Primal Beast
* Hard carries who just want to farm and be left alone will not appreciate Primal Beast, heroes such as Medusa, 
Drow Ranger...
Mars
* Heroes who lack burst damage will have a hard time against Mars: Phantom Lancer, Nature's Prophet, Lich.
Mars
* Heroes with forced movement abilities or non-interrupting forced movement, such as Lion, Drow Ranger, Magnus, Mars, as they can cancel blast-off mid air, removing his ability to initiate or escape.
Mars
* Heroes who can disable Mars but cannot do any damage to him, meaning he just tanks their abilities: 
Doom, Magnus.
Primal Beast
* Any hero who lanes very poorly will struggle with Primal Beast's potential snowball in the very early levels, like Keeper of the Light, Luna, Templar Assassin...
Primal Beast
* Illusion heroes will struggle against Primal Beast's area damage capability, such as 
Chaos Knight, Naga Siren, 
Terrorblade.
Mars
* Heroes that can negate Hoodwink's mobility: Kunkka, Disruptor, Mars.
Primal Beast
* Heroes who rely on burst damage with magical damage will struggle to kill Primal Beast: Spirit Breaker, Gyrocopter, Leshrac
Primal Beast
* Illusion heroes will struggle against Primal Beast's area damage capability, such as Chaos Knight, Naga Siren, Terrorblade.
Primal Beast
* Any hero with low mobility and max healthsuch as 
Silencer, Crystal Maiden etc.
Mars
* Heroes who cannot fight back during Arena of Blood in the early and mid game: Abaddon, Anti-Mage, Broodmother, Luna, Sniper, Troll Warlord, Weaver, Clinkz.
Primal Beast
* Any hero who lanes very poorly will struggle with Primal Beast's potential snowball in the very early levels, like Keeper of the Light, Luna, Templar Assassin...
Primal Beast
* Any hero with low mobility and max healthsuch as Silencer, Crystal Maiden etc.
Primal Beast
* Heroes who cannot escape from Trample early might be easy first blood. Heroes like Witch Doctor and Omniknight should play very cautiously alone...
Primal Beast
* Heroes who rely on burst damage with magical damage will struggle to kill Primal Beast: Spirit Breaker, Gyrocopter, Leshrac
Mars
* Heroes that are hard to gank: Axe, Death Prophet, Phantom Lancer, 
Slark, Centaur Warrunner, Bristleback, Medusa, Mars.
Mars
* Heroes who cannot fight back during Arena of Blood in the early and mid game: Abaddon, Anti-Mage, Broodmother, Luna, Sniper, Troll Warlord, Weaver, Clinkz.
Mars
* Heroes who rely on their target to run away: Riki, Bounty Hunter.
Mars
* Heroes that are hard to gank: 
Dragon Knight, Mars, Centaur Warrunner.
Mars
* Heroes with the capability of removing or destroying trees greatly hinders the effectiveness of Treant Protector's abilities: Batrider, Nature's Prophet, Lina, Enigma, Mars
Mars
* Legion Commander is both good and bad vs Mars, on the plus side she can dispel Spear of Mars with 
Press the Attack and is a good 
Silver Edge carrier. However, Mars is not an ideal 
Duel target, as Bulwark will force her to 1: Buy Silver Edge, and 2: Hit Mars with it before the Duel, allowing a skilled Mars to react, especially with Eul's Scepter of Divinity. In teamfights, Mars will happily draw attention after using his abilities, and tank the Duel with all spells on cooldown.
Mars
* Because Duel requires both combatants to face each other, Bulwark's effectiveness will be increased by a huge margin, which makes it much more difficult for Legion Commander to win any duels against him.
* Spear of Mars and God's Rebuke pushes Legion Commander away during Duels against allies.
Additional:
* Bulwark immensely mitigates Duel, even with bonus physical damage, as Bulwark scales by percentage. Mars can also buy time for a dueled ally by pushing Legion Commander away with Spear of Mars.
Mars
* 
Nether Blast, 
Decrepify and 
Life Drain deal high magical damage and bypasses Bulwark.
* 
Nether Ward reduces the amount of abilities Mars can use during fights and forces Mars to be careful about the heavy mana cost of Arena Of Blood.
* Pugna is one of few heroes that can contest Mars' ability to push and defend towers early on.
Primal Beast
* Primal Beast has multiple ways to cancel Life Drain very quickly.
* Pugna has a very low strength gain and as a support does not have much gold to buy health items, making him vulnerable to Primal Beast's onslaught of magical damage.
* Ironically, Decrepify actually just increases Primal Beast's damage on the targeted ally if Trample is activated. However, it can be used to slow him down and prevent any further Trample damage.
Primal Beast
* 
Shukuchi allows Weaver to have faster movement speed and can outrun Primal Beast in most instances, such as while he is trampling.
* Trample disarms Primal Beast, so casting 
The Swarm can make him vulnerable to ranged attacks. Primal Beast also has an innately slow attack speed and will take a long time destroying the bugs.
* 
Time Lapse allows Weaver to negate and heal burst damage, which Primal Beast is reliant on.
Mars
* Shukuchi cannot help Weaver escape from Arena of Blood, and can most likely die if detected through invisibility.
* If pinned to the arena's walls, Time Lapse tends to not be enough to save Weaver, as God's Rebuke can keep him burst down thanks to its damage scaling.
* The Swarm and 
Geminate Attack are not enough to pierce through Bulwark.
Primal Beast
* Primal Beast's abilities require movement to deal damage, making 
Rupture potentially deadly and debilitating. Furthermore, its initial damage based on the target's current health is devastating to a full-health Primal Beast with his high strength gain and thus high HP.
* Due to his reliance on spells, Primal Beast is vulnerable to Blood Rite's powerful silence without items to counter it.
Mars
* Arena Of Blood prevents Bloodseeker from attacking a Ruptured target.
* Bulwark helps Mars survive Rupture ganks simply by turning towards Bloodseeker without moving.
* Spear of Mars and God's Rebuke can push Bloodseeker from Ruptured targets.
Primal Beast
* Supports who can slow him to the point Trample does very little damage in the lane are also not fun: Lich, Ogre Magi, Winter Wyvern.
Mars
* Heroes who lack burst damage will have a hard time against Mars: Phantom Lancer, Nature's Prophet, Lich.
Mars
* Heroes that can save their allies can be a big problem for Mars: Dazzle, Omniknight.
Primal Beast
* Heroes who cannot escape from Trample early might be easy first blood. Heroes like Witch Doctor and Omniknight should play very cautiously alone...
Mars
* Time Dilation while
Spear of Mars and 
God's Rebuke are on cooldown will make these abilities unusable for a long time, rendering Mars nearly useless.
Bulwark completely.
Time Walk allows Faceless Void to escape or enter Arena Of Blood, and helps him recover from Mars' burst damage.
Time Lock's magical damage ignores Bulwark.
Chronosphere allows Faceless Void to reposition behind Mars, ignoring his Bulwark while he is helplessly frozen in time.
* Mars cannot turn inside the Chronosphere, which makes it easy to attack him from the back, bypassing
Additional:
*
*
*
Primal Beast
*
Time Walk makes it impossible for Primal Beast to stay on top of Faceless Void with his abilities and allows him to heal burst damage dealt to him.
Aghanim's Shard, Onslaught can be easily escaped. He could also choose to get a lower cooldown on Time Walk, making it even harder for Primal Beast to catch him in fights or stop his initiations.
Time Dilation will make Primal Beast useless for an extended time after casting his abilities if he does not have a dispel.
Chronosphere has many uses such as stopping Primal Beast from casting abilities on him or allies or even on a teammate, since Primal Beast has no way to assist allies trapped within the sphere.
* Once Faceless Void has an
*
*